Field of the Invention
The present invention relates to a moldable hydrophilic polymer composition, preferably gelatin, for use in an injection molding device preferably with a microprocessor, to produce capsules. The present invention utilizes gelatin made from various types of gelatin, including acid or alkaline processed ossein, acid processed pigskin, or alkaline processed cattle hide. Said types of gelatin have a molecular mass range of 10,000 to 2,000,000 Dalton or a molecular mass range of 10,000 to 2,000,000 and 10,000,000 to 20,000,000 Dalton. The method for determination of the molecular mass distribution of the various types of gelatin used in the present invention is described in the following references:
I. Tomka, Chimia. 30, 534-540 (1976) PA0 I. Tomka, et al, Phot. Sci. 23, 97 (1975)
Gelatin having a molecular mass range between 10,000 and 2,000,000 Dalton, was found to give less deformation of capsule parts after ejection from a capsule mold,
When in the following description the term "gelatin" is used, other hydrophilic polymer compositions whose properties are acceptable as capsule materials are also included. Hydrophilic polymers are polymers with molecular masses from approximately 10.sup.3 to 10.sup.7 Dalton carrying molecular groups in their backbone and/or in their side chains and capable of forming and/or participating in hydrogen bridges. Such hydrophilic polymers exhibit in their water adsorption isotherm (in the temperature range between approximately 0.degree. to 200.degree. C.) an inflection point close to the water activity point at 0.5. Hydrophilic polymers are distinguished from the group called hydrocolloids by their molecular dispersity. For the maintenance of the molecular dispersity of said hydrophilic polymers a fraction of water--according to the working range of the present invention--of 5 to 25% by weight of said hydrophilic polymers must be included provided that the temperature of said hydrophilic polymers is in the working range between 50.degree. C. and 190.degree. C. of the present invention.
There are other hydrocolloids, not hydrophilic polymers in the sense of this definition, which contain more or less spherical or fibrous particles whereby those particles are composed of several macromolecules of a hydrophilic polymer within the molecular mass range of 10.sup.3 -10.sup.7 Dalton giving rise to particle sizes between 0.01-10 microns which is the typical range of colloidal particles. It is a primary object of the present invention to utilize hydrophilic polymer compositions in the production of capsules.